1. Field of the Invention
The present invention relates to a method and an apparatus for determining types of digital versatile discs, and more particularly to a method and an apparatus for determining DVD-ROM, DVD− and DVD+ types of digital versatile discs.
2. Description of the Related Art
Digital versatile discs (DVDs) available in the market include a read-only-memory (DVD_ROM) type, from which data can only be read, and another type in which data can be written/burned. The data-burnable DVDs include DVD− and DVD+ based on different specifications. Most DVD players are compatible in different specifications. Therefore, how to determine a type of a disc has become an essential technique.
The conventional method is to use position data contained in pre-groove wobble signals to determine the types of DVDs. According to the specifications of DVDs, DVD-ROM does not contain wobble signals. In contrary, DVD− and DVD+ contain not only normal tracks but also wobble signals. The source of these signals is shown in FIG. 1. When a disc spins in a DVD player, the pick-up head 101 slides outwardly along the track 102 as shown in FIG. 1. Photo diodes of the pick-up head 101 are arranged as shown in FIG. 1. These areas A, B, C and D sense signals with different intensities. Accordingly, wobble signals can be generated according to the following formula:G×[g1×(A+D)−g2×(B+C)]
Wherein, G, g1 and g2 are adjustable gains.
DVD− and DVD+ have position data which are contained in wobble signals and can be decoded by logic operational circuits in order to obtain the present position data. FIG. 2 is a schematic drawing showing a wobble signal of DVD+. The wobble signal 201 includes plural phase change regions 202. The position data can be obtained from the wobble signal 201 after the wobble signal 201 is decoded by the logic operational circuit. FIG. 3 is a schematic drawing showing a wobble signal of DVD−. The wobble signal 301 includes plural land per-pits 302. Similarly, the position data can be obtained after the wobble signal 301 is decoded by the logic operational circuit. From FIGS. 2 and 3, it can be seen that for different wobble signals of DVD+ and DVD−, the decoding functions of the logic operational circuits are also different. Accordingly, they can be used to determine the types of DVDs.
FIG. 4 is a flowchart showing a conventional method for determining a type of a digital versatile disc. First, in step 402, it is assumed that the loaded disc is DVD+, and the parameters for DVD+ are set. In step 404, determining whether the present position data are successfully accessed. If the data can be accessed, it is determined the disc is DVD+ in step 406. If not, it is assumed the disc is DVD− in step 408, and the parameters for DVD− are set. In step 410, determining whether the present position data are successfully accessed again. If the data can be accessed, it is determined the disc is DVD− in step 412. If not, it is determined the disc is DVD-ROM in step 414.
The disadvantage of this method is that the parameters of DVD+ and DVD− must include parameters of most discs, especially for burned discs. Since the quality of position data on burned discs become worse, false determination is very likely to occur. Accordingly, a new method is desired to resolve the issue and enhance the probability of correctly determining the types of DVDs.